For an old electronic design I'm looking for a replacement of an
obsolete component (TCA520B)
Which component is the best replacement for the TCA520B?
It looks as if your biggest problem is the pin out arrangement. A ua709 is
close (if you can get one of those either) it has input frequency
compensation pins instead of offset adj pins.
Its doubtful that the TCA520B is anything special - just clip pins 1, 5 & 8
off a 741, or if the offset adjust is needed don't clip pin 1 and wire pin 5
to hole 8 on the pcb.